CMSC131
Fall 2004
Midterm #1
Grader Use Only:
#1
(35)
#2
(20)
#3
(20)
#4
(25)
Total
First Name: _______________________
Last Name: _______________________
Student ID: _______________________
Section time (10am/11am) ___________ TAs: __________________________
I pledge on my honor that I have not given or received any unauthorized assistance on this
examination.
Your signature: _____________________________________________________________
General Rules:
 This exam is closed-book and closed-notes.
 Write your answers in the space provided. If you need additional space, raise your hand.
 If you have a question, please raise your hand.
 Total point value is 100 points. Point values attached to individual problems are subject to
possible (minor) changes.
 Good luck!
1
(100)
Problem 1 (35 pts)
a. (4 pts) Which of the following are valid Java identifiers? (Circle the valid ones.)
Car
$chultzie
per%cent
_22Skidoo
b. (2 pts) Are the following two identifiers considered the same? Yes / No. (Circle one)
temperature
TEMPERATURE
c. (2 pts) What value is assigned to a reference variable to indicate that it refers to NO object?
(Circle one.)
i. null
ii. 0 (zero)
iii. "" (empty string)
iv. JOptionPane.NO_OBJECT
d. (2 pts) How many distinct String object instances are created in the following code segment?
String s1 = new String("Hello");
String s2 = "GoodBye";
String s3 = s1;
Answer:_______
e. (2 pts) (Fill in the blank) The special area of memory where object instances are created and
stored is called the ______________________________________
f. (5 pts) Which of the following are NOT Java primitive types? (Select all that apply.)
i. integer
ii. exponential
iii. int
iv. Float
v. String
g. (2 pts) As described in lecture, the software development lifecycle has five phases (parts).
Name ANY TWO of them. (You do not need to describe them.)
________________________________
_________________________________
h. (4 pts) Give a single Java statement (using System.out.println) that outputs the following line:
Bob said, "It's C:\WINDOW"
___________________________________________________________________________________
2
i. (4 pts) For each of the following declaration/initialization statements, indicate whether it is
valid or invalid according to Java's rules on assigning types. (Circle the correct answer
in each case.)
int i = 4L;
VALID / INVALID
boolean b = 0;
VALID / INVALID
float f = 1.75;
VALID / INVALID
double d = 2.0E-4;
VALID / INVALID
j. (6 pts) Add parentheses to specify completely the order in which the following expressions
will be evaluated. You do not need to specify the final value of the expressions. The
variables associated with the expressions are:
int w =
int x =
int y =
boolean
10;
20;
30;
b;
b
=
w
<
x
&&
y
<
ii. x
=
w *=
y
++
-
2
iii. y
=
- x
- y
*
5
i.
+
30
;
Note: Add parentheses only.
DO NOT evaluate.
;
%
3
;
k. (2 pts) What will occur if the following code segment is executed? Briefly explain (in one or
two sentences).
String s = "Summer";
s = null;
System.out.println( s.length() );
Answer:
3
Problem 2 (20 pts)
Show the output produced by each of the following program segments. (Be careful. We have
hidden some traps!)
a. (10 pts)
int
int
int
int
x
y
w
s
=
=
=
=
b. (10 pts)
int x = 7;
while (x > 0) {
System.out.println(x);
x -= 2;
}
System.out.println(x);
1;
1;
10;
21;
if( (x == 1) || ( y++ > 1) )
x++;
System.out.println(x);
System.out.println(y);
System.out.println(w += 2);
System.out.println(s % 10);
if (s > 30 && true)
if (s / 2 > 10)
System.out.println("One");
else
System.out.println("Two");
System.out.println("Three");
4
Problem 3 (20 pts)
For each of the following parts, give a code fragment to achieve the given task. In each case we
have given variable declarations, but we have intentionally not given the values of the variables.
You may declare additional variables if needed.
a.
(5 pts) You are given three variables x, y, z, declared as shown below. Give a code
fragment that does the following. If x is negative (less than 0), it assigns z to be the sum of
x and y. Otherwise, it assigns z to be the maximum of x and y. You may not use any
methods from the Java class library
long x = ...;
int y = ...;
double z;
/* Write your code fragment below */
b. (5 pts) You are given two variables d and e below, each of type int, and the third variable b
of type boolean. Give a code fragment that sets b to true if d and e are both even or both
odd, and sets b to false otherwise.
int d = ...;
int e = ...;
boolean b;
/* Write your code fragment below */
5
c. (5 pts) You are given a variable q of type float. Give a code fragment that modifies q so
that it is truncated to only two decimal places. For example, if q had been 123.6789, after
your fragment is finished, q will have the value 123.67. You may not use any methods
from the Java class library. (Hint: First multiply q by 100.)
float q = ...;
/* Write your code fragment below */
d. (5 pts) You are given four variables, a, b, c, and max, all of type float. Give a code
fragment that assigns max to be the maximum of a, b, and c. For example, if these
variables contained the values 17, 2, and -92, then max would be set to 17. You may not
use any methods from the Java class library.
float a = ...;
float b = ...;
float c = ...;
float max;
/* Write your code fragment below */
6
Problem 4 (25 pts)
Write a complete Java program that computes the numeric average of a set of scores. Your program
will read the number (as an integer) of scores to process, followed by the actual scores (as doubles),
and will print the numeric average of these scores. For example, if we wanted to compute the
numeric average of
50.5
49.5
40.0
60.0
we would first input the value 4 (number of scores), then input each of the scores. The output of
the program is a message that uses the following format:
Average: numericAverage
where numericAverage denotes the computed average.
For the above example the output would be:
Average: 50.0
The following specifications apply to this problem:







Use the prompt string “Enter Number” to read the number of scores.
Use the prompt string “Enter Value” to read each score value.
Use JOptionPane method for input and output operations.
Each number will be read using a separate call to JOptionPane.
The name of the class will be ComputeAvg.
You may assume that all inputs are valid, and the number of scores is 1 or greater.
Meaningful variable names are NOT required. Try to maintain good indentation.
.
WRITE YOUR PROGRAM ON THE NEXT PAGE.
7
8
WRITE YOUR SOLUTION TO PROBLEM 3 ON THIS PAGE.
9